A 300 PIN MSA 40 Gb TRANSPONDER protocol, i.e., REFERENCE DOCUMENT FOR 300PIN 40 Gb TRANSPONDER, requires that a single board can provide an Adaptable Power Supply (APS) for the 300 PIN MSA 40 Gb TRANSPONDER, wherein a voltage range of the APS is 1.2V to 2.5V. This protocol provides a connection block diagram of the APS and the 300 PIN MSA 40 Gb TRANSPONDER, as shown in FIG. 1. According to the protocol, pins between the APS and the 300 PIN MSA 40 Gb TRANSPONDER comprise 4 signals, which are respectively APS Digital, APS SENSE, APS SET and GND. The APS Digital is used for supplying power to the 300 PIN MSA 40 Gb TRANSPONDER. The APS SET is used for setting an adjustment point of an output voltage of the APS. The APS SENSE signal is used for providing remote sensing for an output voltage (APS POWER). Correspondingly, there are 4 pins between the APS and the 300 PIN MSA 40 Gb TRANSPONDER, respectively being an APS Digital pin, an APS SENSE pin, an APS SET pin and a GND pin.
As shown in FIG. 2, FIG. 1 can be simplified in order to facilitate the prediction and understanding. A calculation formula of VAPS—Digital can be obtained from FIG. 2:VAPS—Digital=Vsense×R3/(R2+R1)+Vsense  formula (1)
As shown in Table 1, the protocol regulates a corresponding relationship between an output VAPS—Digital and a resistor R1.
TABLE 1R1 resistance value (Ω)Vout (V)15301.26721.53301.802.5
The Vout in Table 1 is VAPS—Digital. According to the corresponding relationship between the R1 resistance value and the VAPS—Digital regulated in Table 1, the 300PIN 40 Gb TRANSPONDER protocol provides a parameter selection, which can satisfy the corresponding relationship, as follows: Vsense=0.8V, R2=470Ω, R3=1000Ω. If only using a power control chip, of which a reference voltage (namely, Vfeedback in the figure) is 0.8V, to supply power to the 300 PIN MSA 40 Gb TRANSPONDER, a selection range of the power control chip is too narrow.